Bought new AX3200 RB01 EU/global version and flashed openwrt via Xmir patcher. Telnet was disabled in stock fw.
Stock fw was 1.0.83 but I don't know which uboot it has.
I have env print from the stock fw and the backup of all mtd blocks, made with xmir.
Using it for a dumb AP and would like to be sure it is not going to brick itself later 
@remittor
In your post values of these flags are different for 2 uboot versions (0 vs 8):
This is my nvram values, restarted a couple of time and the above two counters do not increase.
Am I safe?
root@OpenWrt:~# fw_printenv | grep -E 'boot_fw|flag_|ssh|uart|boot_wait|success'
boot_fw0=run boot_rd_img;bootm
boot_fw1=run boot_rd_img;bootm
boot_wait=on
bootargs=console=ttyS0,115200n1 loglevel=8 swiotlb=512 rootfstype=squashfs firmware=1 uart_en=1
bootmenu_0=1. Load firmware 0 and bootup.=run boot_fw0
bootmenu_1=2. Load firmware 1 and bootup.=run boot_fw1
flag_boot_rootfs=1
flag_boot_success=1
flag_boot_type=2
flag_last_success=1
flag_ota_reboot=0
flag_try_sys1_failed=0
flag_try_sys2_failed=0
ssh_en=1
uart_en=1