1. Python.
2. Flask. Pure server-rendered HTML, no fancy frontend. Avoid JS as long as I can, just use jinja templates. If my app is not going to work with good old HTML and CSS chances are it's not going to work at all.
3. Classless CSS framework. I like this: https://watercss.kognise.dev/.
4. Sqlite3 or Postgres. Prefer postgres because with docker it's 5 minutes to set up. I use SQLAlchemy from the start because it makes life easier. If you ever deploy and worry about real data you add alembic for migrations.
5. One docker compose for everything.
6. Cheap VPS for like $3 per month.
That's it. I would like to upgrade my MVP stack, but it's battle-tested and it works well. After the 9 to 5 I only have like 3 brain cells alive so I need to get stuff done as fast as possible, which means using what I know.
One thing I often reinvent and reimplement is OAuth. Definitely "Sign in with google" is the best way to add auth to your app, but it's such a pain to set up.