Upgrading to the regular OpenWRT
As I understood, the router comes with some kind of proprietary OpenWRT version, and I saw some topics about issues with upgrading it to the latest regular version (Filesystem issues?). I also saw there were few PRs about it. The information on the device page is not so clear, and looks a bit outdated.
Can someone shed some light about the upgrade process? Can I just upgrade from the stock "proprietary" OpenWRT to the regular 20.02.1 release image from LuCi?
I plan to by the version with DualBand modules (U7603E-H1 + U7612E-H1) - Are they properly supported?
As much as I like the MT7623, the unit you have in the link uses the MT76 driver (7603 and 7612). They are supported and still under development in OpenWrt, they are not the best. Since you mentioned 1Gbit WAN why don’t you look at something like this;
Keep the Archer C7 as “dump” WiFi access point and have a combination that will do “anything”. The N3450 comes with AES-NI and with 4GB ram and like 32GB msata (ssd) it wil be way more future proof (next step would be 10Gb Ethernet).
But your question: yes you should be able to do a system upgrade.
mt7623 is a rather exotic Mediatek platform (ARMv7, instead of ARMv8, as mt7622 would offer), with few supported devices and few eyes taking care of it. If a device isn't explicitly listed in OpenWrt's ToH, then there likely isn't any support for it and you'd have to develop it yourself.
1 GBit/s routing performance might be a bit much to ask for as well.
Thanks all for your comments.
Regarding the option of using N3450 and the TP-Link as access point - this might be a nice option, although I can't find the N3450 or N4200 on the ToH - where can I find information about it with OpenWRT (how to install, what is supported, etc.)?
Regarding the MT7623 being an exotic platform - is there any other similar router that is recommended for my use-case?
I can compromise on the 1Gbps WAN requirement, which is BTW not symmetric. My current ISP package is for 500Mbps download and 50Mbps download but I would like to upgrade to 1000Mbps download with 100Mbps upload.
Currently with my TP-Link I'm getting ~200-250Mbps only (as it can't do HW NAT with OpenWRT).
As the TOH page says, you can upgrade from the vendor firmware (or from OpenWrt 19.07) using the 'legacy' image. That preserves the vendor's U-Boot and the hard-coded partitioning on the command line. You can then upgrade using the full-eMMC image which sets up the partition table properly and starts using it, as well as our own U-Boot. Upgrading should work fine, and we keep an image of the vendor firmware around for reflashing and testing that.
These are actively maintained by Mediatek in the upstream kernel and I believe they work fine. The one to avoid is the MT6625 in (e.g.) the Banana Pi R2.
If that's still happening, it's almost certainly not a platform-specific issue; it'll be an issue with F2FS. Using ext4 as suggested there is probably a good way to avoid it.