There are quite a few factors that would matter (e.g a 100% tech crowd is going to understand that youname.app is valid whereas a non-tech crowd might think it's yournameapp.com).

Generally, I'd go with the below:

1. .com

2. slightly longer .com (e.g bobsmith.com is taken, so go with bobMIDDLENAMEsmith.com).

3. something relevant (e.g .tech, .accountant, etc).