Hello there, I need some tips and direct suggestions for modems where open source software can be installed, to be used with openwrt routers
What kind of modem?
ADSL / VDSL?
3g / 4g / 5g?
I can probably come up with a couple more...
Ah sorry, I am a newbie, it needs to be Wifi modem or modem/router
Still doesn't answer the question.
3g/4g capability Wifi, cables only as a backup. Something along the lines of this: https://freemeshwireless.com
you have two options.
Ether buy a device with the modem built in, or one where the modem is attached via the USB port.
I'd go for the latter.
USB LTE modems are cheap (or at least used to be, before Corona), you can/could get a 4G unit without simlock for 10-15€ on ebay.
I have a Huawei e3276, which works really well with OpenWRT, connected via the USB-port.
When it comes to the router, whatever's supported by Openwrt, got at least 8MB flash space and 128MB RAM (the bigger the better), and at least one USB-port.