Amazing you'd suggest an R4 given it's support is fundamentally broken.
Sinovoip's OEM build is an ancient 21.02 one. Whereas in the official one wifi is completely broken, working SFP is pure luck as "many" modules (all four fiber ones I've got here) on kernel 6.6 either don't show at all or just fail to come up. This was known to OpenWrt's mediatek maintainer who preferred to "spot and fix" it on the go:
Meanwhile there are about two kernel devs working on mediatek in their free time who've only begun upstreaming R4 support, eg. Frank W.'s DTS parts… for kernel 6.14. (The other dev is Eric. W.)
To quote Frank W.:
"The patches i posted are mainly patches adding basic support,only slightly changed to get accepted for mainline. There is no network part yet,also no sfp. Maybe i add sfps in next round,but without full network part (which is much work) it will not work."
( https://forum.banana-pi.org/t/bpi-r4-and-sfp/16945/330 )
Edit: The R4 also needs a soldering mod for certain SFP modules, and prior board revs have resistors that break SFP if NVMe is present (I'd say: sure to get 1.1, but Sinovoip originally shipped that rev broken as well, and didn't increment to 1.2 for the fixed ones).
OpenWrt One is based on Banana Pi anyway. And it comes already assembled, with the Luci GUI working out of the box, etc. In other words, it is a nice package for those who DON'T want to any screwdrivers to be involved just to get it actually running in your home.
Over the last few years I had several spare routers laying around. Never had I one that I could flash like you described.
All had memory or RAM limitations. Maybe the spare routers I had are just too old.
R5s has a garbage CPU that won't be able to handle QoS on probably >250mbps.
I'd avoid anything arm based that doesn't have a7x cores (ideally a76/a78 or newer, though I don't think there's any SBC socs using the a710/715/720 yet). A55 cores are old stupidly slow efficiency cores (area efficient, not power efficient).
