Lawrence Kesteloot has put up a web site called https://www.my-trs-80.com/ which emulates a Model III TRS-80 and has some sample software and access to the retrostore.
If you create an account and log in you can store your own software there.
One of the many features to note is that if you are programming in BASIC you can click a button to extract the program to a full screen text editor for purposes of easy editing.
This is the same Lawrence who developed the cassette reader/cleaner utility and web site, located at https://github.com/lkesteloot/trs80-cassette-reader-js.
Excellent work, Lawrence!