hi! sorry if it's long and broken english,
i'm experiencing a slow down on the latest firmware(25.12.2) on both wifi and the ssh itself when i'm using the lan cable it's working fine on internet speed and ssh interface itself slightly responsive than using wifi, so i decide to downgrading it into older firmware and the one that really got it stable now for wifi and ssh is fw 23.05.6. when i use the latest fw the wifi can't get into full speed, it stuck around 30megabit and the speed itself are just trash really unstable.
sometimes the wifi would slowdown to a crawl and in some instance the wifi just dissapear when another device use the wifi for streaming or downloading (my isp is 50 megabit). but after downgrading to 23.05.6 the wifi had the same speed as on ethernet cable from the mi router (50 megabit) and the wifi itself now stable,
i tested it with my laptop while streaming/uploading(both using full speed peak at 50megabit) connected to the wifi while on my phone i test fast.com and it's still able to get 20mb leftover bandwith, for now i'll able to stream video or even ssh into it when someone else using the full bandwith for streaming/download/uploading and no more sudden disappearing wifi..
my question now is why on the latest fw (25.12.2) the wifi slow and unstable? is it bug or something broken in the driver or code? i also use dnsproxy baked into the fw using firmware-selector website. but i don't think this was the culprit, like i said i'm downgrading it to 23.05.6 with dnsproxy and everything is now stable with full load on the wifi. i used this router as dumb ap + block ads and unblock blocked website from the isp hence the need for dnsproxy, i don't even know how to debug this but if anyone with more knowledgeable than me and have mi4c router could anyone confirm that it wasn't just me that has this problem, and yes offloading are enable using hardware offload, thanks! 
The only way to know for sure what is happening is to review your configuration.
To be clear, 23.05 shouldn't be used -- it's EOL and unsupported. 24.10.6 was released recently, so this is a better comparison point in terms of performance while still being on a supported version.
Let's see your complete config -- ideally from 25.12.
Please connect to your OpenWrt device using ssh and copy the output of the following commands and post it here using the "Preformatted text </> " button (red circle; this works best in the 'Markdown' composer view in the blue oval):
Remember to redact passwords, VPN keys, MAC addresses and any public IP addresses you may have:
ubus call system board
cat /etc/config/network
cat /etc/config/wireless
cat /etc/config/dhcp
cat /etc/config/firewall
here's the whole config and the system info i believe, i actually don't configure much because i reset my whole config just to know if it is my config or not so i just use the default config and replace stuff, but it still slow and unstable in newer fw, this config is from 25.12.2 but i just used it in 23.05.6(downgrade it without erasing the config) i don't think my issue was the config but hey i could be wrong
system board
{
"kernel": "5.15.189",
"hostname": "XXX",
"system": "MediaTek MT7628AN ver:1 eco:2",
"model": "Xiaomi Mi Router 4C",
"board_name": "xiaomi,mi-router-4c",
"rootfs_type": "squashfs",
"release": {
"distribution": "OpenWrt",
"version": "23.05.6",
"revision": "r24232-539228933c",
"target": "ramips/mt76x8",
"description": "OpenWrt 23.05.6 r24232-539228933c"
}
}
network
config interface 'loopback'
option device 'lo'
option proto 'static'
list ipaddr '127.0.0.1/8'
config globals 'globals'
option dhcp_default_duid '*'
option ula_prefix '*::/48'
option packet_steering '1'
config device
option name 'br-lan'
option type 'bridge'
list ports 'eth0.1'
config interface 'lan'
option device 'br-lan'
option proto 'static'
list ipaddr '192.168.1.1/24'
option ip6assign '60'
config device
option name 'eth0.2'
option macaddr '*'
config interface 'wan'
option device 'eth0.2'
option proto 'dhcp'
config interface 'wan6'
option device 'eth0.2'
option proto 'dhcpv6'
config switch
option name 'switch0'
option reset '1'
option enable_vlan '1'
config switch_vlan
option device 'switch0'
option vlan '1'
option ports '4 2 6t'
config switch_vlan
option device 'switch0'
option vlan '2'
option ports '1 6t'
wireless
config wifi-device 'radio0'
option type 'mac80211'
option path 'platform/10300000.wmac'
option band '2g'
option channel 'auto'
option htmode 'HT20'
#option country 'ID'
option cell_density '0'
config wifi-iface 'default_radio0'
option device 'radio0'
option mode 'ap'
option ssid '*'
option key '*'
option wpa_disable_eapol_key_retries '1'
option network 'lan'
option encryption 'psk2+tkip+ccmp'
option disassoc_low_ack '0'
option skip_inactivity_poll '0'
dhcp
config dnsmasq
option domainneeded '1'
option boguspriv '1'
option filterwin2k '0'
option localise_queries '1'
option rebind_protection '1'
option rebind_localhost '1'
option local '/lan/'
option domain 'lan'
option expandhosts '1'
option nonegcache '0'
option cachesize '10000'
option authoritative '1'
option readethers '1'
option leasefile '/tmp/dhcp.leases'
option resolvfile '/tmp/resolv.conf.d/resolv.conf.auto'
option nonwildcard '1'
option localservice '1'
option ednspacket_max '1232'
option filter_aaaa '0'
option filter_a '0'
option noresolv '1'
option min_cache_ttl '3600'
option max_cache_ttl '86400'
list server '127.0.0.1#5354'
list server '::1#5354'
config dhcp 'lan'
option interface 'lan'
option start '2'
option limit '254'
option leasetime '1h'
option dhcpv4 'server'
option dhcpv6 'server'
option ra 'server'
option ra_slaac '1'
list ra_flags 'managed-config'
list ra_flags 'other-config'
config dhcp 'wan'
option interface 'wan'
option ignore '1'
config odhcpd 'odhcpd'
option maindhcp '0'
option leasefile '/tmp/odhcpd.leases'
option leasetrigger '/usr/sbin/odhcpd-update'
option loglevel '4'
option piodir '/tmp/odhcpd-piodir'
option hostsdir '/tmp/hosts'
firewall
config defaults
option syn_flood '1'
option input 'REJECT'
option output 'ACCEPT'
option forward 'REJECT'
option flow_offloading '1'
option flow_offloading_hw '1'
config zone
option name 'lan'
list network 'lan'
option input 'ACCEPT'
option output 'ACCEPT'
option forward 'ACCEPT'
config zone
option name 'wan'
list network 'wan'
list network 'wan6'
option input 'REJECT'
option output 'ACCEPT'
option forward 'DROP'
option masq '1'
option mtu_fix '1'
config forwarding
option src 'lan'
option dest 'wan'
config rule
option name 'Allow-DHCP-Renew'
option src 'wan'
option proto 'udp'
option dest_port '68'
option target 'ACCEPT'
option family 'ipv4'
config rule
option name 'Allow-Ping'
option src 'wan'
option proto 'icmp'
option icmp_type 'echo-request'
option family 'ipv4'
option target 'ACCEPT'
config rule
option name 'Allow-IGMP'
option src 'wan'
option proto 'igmp'
option family 'ipv4'
option target 'ACCEPT'
config rule
option name 'Allow-DHCPv6'
option src 'wan'
option proto 'udp'
option dest_port '546'
option family 'ipv6'
option target 'ACCEPT'
config rule
option name 'Allow-MLD'
option src 'wan'
option proto 'icmp'
option src_ip 'fe80::/10'
list icmp_type '130/0'
list icmp_type '131/0'
list icmp_type '132/0'
list icmp_type '143/0'
option family 'ipv6'
option target 'ACCEPT'
config rule
option name 'Allow-ICMPv6-Input'
option src 'wan'
option proto 'icmp'
list icmp_type 'echo-request'
list icmp_type 'echo-reply'
list icmp_type 'destination-unreachable'
list icmp_type 'packet-too-big'
list icmp_type 'time-exceeded'
list icmp_type 'bad-header'
list icmp_type 'unknown-header-type'
list icmp_type 'router-solicitation'
list icmp_type 'neighbour-solicitation'
list icmp_type 'router-advertisement'
list icmp_type 'neighbour-advertisement'
option limit '1000/sec'
option family 'ipv6'
option target 'ACCEPT'
config rule
option name 'Allow-ICMPv6-Forward'
option src 'wan'
option dest '*'
option proto 'icmp'
list icmp_type 'echo-request'
list icmp_type 'echo-reply'
list icmp_type 'destination-unreachable'
list icmp_type 'packet-too-big'
list icmp_type 'time-exceeded'
list icmp_type 'bad-header'
list icmp_type 'unknown-header-type'
option limit '1000/sec'
option family 'ipv6'
option target 'ACCEPT'
config rule
option name 'Allow-IPSec-ESP'
option src 'wan'
option dest 'lan'
option proto 'esp'
option target 'ACCEPT'
config rule
option name 'Allow-ISAKMP'
option src 'wan'
option dest 'lan'
option dest_port '500'
option proto 'udp'
option target 'ACCEPT'
config redirect 'dns_int'
option name 'Intercept-DNS'
option family 'any'
option proto 'tcp udp'
option src 'lan'
option src_dport '53'
option target 'DNAT'
update:so the new 25.12.3 is out tried it aaannd the wifi still unstable,
still stuck in 30Mbps and the speed itself got really unstable when i tried to download and upload at the same times using my laptop, the download speed goes as low as 5.6Mbps. also bootime took ages too!, almost 2 minutes until it fully booted and then the wifi would appear around 45 second after it boot up. back to 23.05.6 yet again 
something must've been broken in the code itself!