You can easily install openwrt on most of MikroTik routers. Rb5009 is also supported now if you need more powerful router.

https://openwrt.org/toh/mikrotik/rb5009ug_s_in

Four devices is not "most". You had me excited that I might be able to abandon the proprietary UIs on my CRS326/CSS326. And I know those aren't the "real router" devices, but Mikrotik certainly refers to them as routers.

Here is complete list -> https://toh.openwrt.org/?view=normal

78 devices in total when you filter for mikrotik -> brand column.

Oh damn. I had just gone up one level from your first link (to https://openwrt.org/toh/mikrotik/start) and saw a small list of 4. RB450 was on there (which I used to run), so I figured it was mostly accurate.

That table is a much longer list! Still no love for my CRS/CSS, but it does look like that's probably most of the RB devices that Mikrotik actually intends for use as routers (rather than L3 switches).

Interesting, didn't check this url before. https://openwrt.org/toh/start

Also has supported release version column, which is useful to have.