Researching the use of two undocumented Unielec/Aliexpress boards - U7621-02 / U7622-02

Hi all!

So I've been looking around for some new equipment to try for my ongoing mobile router project. I've found a couple promising boards on Aliexpress by Unielec which already has some boards supported by OpenWRT proper. However the models I'm looking at are conveniently not listed but 'close enough' to others in theory.

U7621-02-AX = MTK MT7621 Enterprise Wireless Dual band WIFI6 AX1800 Router LTE 4G 5G OpenWrt Gigabit Dual Sim Card PCBA ODM OEM Board (aliexpress.us)
U7622-02 = MTK MT7622 Enterprise Wireless WIFI Router Dual 4G/LTE 5G OpenWrt Gigabit chipset PCBA ODM OEM Board U7622-02 (aliexpress.us)

The first seems close enough to the U7621-01 that's already supported. Visually (purely based on what's in the listings) the main difference seems to be the one USB port on the 01 was shifted to one of the M.2 slots on the 02.

The second one doesn't have anything in the same family with official support but there is an MT7622 RFB1 build and their OpenWRT screenshot references RFB1 in its model name. Admittedly I have zero clue what this all means other than the name match.

I have read over the wiki regarding the process to add a new device (and I understand this likely doesn't cover every possibly corner case in the process, just the basics) and that combined with the fact these boards already come with their own OpenWRT fork and can likely be reverse engineered, it doesn't seem TOO insurmountable on the surface to tackle with the former likely being the easier of the two but the latter I'd ideally like to have a go at. And all the chips on these boards seem to be supported as well. Just seems like getting the proverbial puzzle pieces together.

So I guess I'm reaching out to see if maybe someone else has looked at these before and maybe has experience? Any Gotchas or tips as far as trying to get these going with the official OpenWRT codebase? This'll likely be a side project to toy around with in my free time. Ultimately my goal for this little hobby project has been trying to find a device that I can run at least 2 WWAN cards (preferably 3 to cover all 3 carriers here in the US, but outside of the 7622 which would need some small tweaks to use the mPCIe slot, those seem to be absolutely unobtanium) and a number of these boards seem to hit a lot of checkboxes.