I’ve never tried it myself but Grist looks like it could fit your needs.

Leaflet is probably the most common JS library for embedding OpenStreetMap into a website. OSM also has a wiki page regarding other options.

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Might FreeCAD be an option?

If you do only web and mail you could consider a web space instead of a VPS. For example Netcup.eu offers packets which include email, Ionos offers one mail account per user account too I think.

Also as you said self hosting emails is quite some pain because Gmail, Microsoft etc blacklist small mail servers rather quickly. Depending on your motivation you could also use Protonmail or mailbox.org as mail provider with your own domain.

Anyway, Debian is a solid choice due to long support times.