it’s not FOSS (it is ‘free to use’ at home) or a ‘server’ application (it’s a windows application), but i just use mailstore home to create and update a local archive of a gmail account. its dot.net requirement is minimal (v4.8 or higher) but i have not yet tried to run it with wine, as i have a separate box that runs windows stuff.
https://www.mailstore.com/de/produkte/mailstore-home/
https://www.mailstore.com/en/products/mailstore-home/
last one i bought new was a 5670, early 2010. was about $75 for what was at that time the best you could get that didn’t need extra power. it was by far the most expensive part in the pc (which i still have and use) i put together back then (sales and substantial rebates were everywhere back then)
the last one before that, and only other one i bought new at retail, was an old agp ati aiw card for a pc-based dvr. i still have that system too, but it’s long been obsoleted by digital hd tv and digital encrypted cable that requires their equipment.
usmobile.com does a cellular-based ‘home phone’ (base station you connect a traditional POTS phone to) for about the same ($9.99/mo, $99/yr), plus hardware at about $100. walmart does the same (via ‘straight talk’) at $15/mo and about $50 for the hardware. no internet needed for the service as they use cellular.