USB (or any kind of PC fax modem) will have the same issues with VOIP lines as a regular fax. PC based faxes use the same methods as standalone units.

I'd be surprised if you could not get one to work with Windows 10. Drivers maybe an issue only. A serial fax modem would work though.

Surely there are services that will do this for a more reasonable fee?

100 pages is a lot of faxing though. Is that realistic as it seems per page is the rate.

$1.50 / page so ok for 2 or 3 but not for 100 pages:
https://www.onetimefax.com/send-a-fax-inside-the-u-s-a.php

What about $3.29 / month for 25 pages and $0.10/page after that?
https://www.srfax.com/pricing/home-fax-to-email-plans/

Free (not sure how) for only a few pages, but also 30 pages for $3 or you can buy credits e.g. 300 pages for $20 making a 100 page fax cost ~$6.60 which I think is reasonable and a 5 pager would be ~$0.30.:
http://www.gotfreefax.com/

Free for short faxes or $1.99 for a 25 page fax.
https://faxzero.com/

So the going rate is a few dollars for a one off 20-30 page fax. I think that's not unreasonable. If you really have to send a 100 page fax, break it down to 3 or 4 groups mark it appropriately as "1 of 4" etc. I know I'd prefer not to have to do that for something like an insurance claim so I'd look for something like that GotFreeFax mob with a non expiring credit.

http://www.tomsguide.com/us/best-online-fax,review-2124-9.html
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)