In this case I would download the deb from here (Click on Mantic, and scroll down to files and find your architecture you use and download the file : packages.ubuntu.com/search?keywords=libfreerdp2 and install it with dpkg -i If that installs successfully then continue your upgrade attempt.
What phone should I buy for max 150.- (around 180$) second hand?
e.foundation by means of Murena sells phones with /e/os installed. Cheapest currently at discount about $200 but is out of stock last time I looked. e.foundation did sell refurbished phones (and does ?) but the price were always over $200 I think.