Tons of options, some more "lock-in" than others. But the stuff you're talking about in general is really not that much lock-in.

For secrets, I personally use Github for that and you can add them in as a build step. Google also offers this: https://cloud.google.com/functions/docs/configuring/secrets

For logging, I just use Google's logging layer. If I was to migrate somewhere else, I'd just use that logging layer.

For releases, I just used github releases as part of my build step. But google also has the concept of releases... https://cloud.google.com/functions/docs/deploy

and on and on...

None of these are major lock-in problems though... any other PaaS platform you want to go to will need those sorts of things too.

That "not that much" easily turns into months or years of migration once you put enough data into it. Cloud providers are showering startups with credits not due to their inherent kindness - they know once you're in it's tough to move out and you are seriously downplaying the amount of effort and costs involved here.

It isn't expensive to run on Cloud Functions at all. You do it right and it scales pretty insanely high with very little additional cost. I've built multiple successful businesses with AppEngine and CF, so I'm keenly aware of their implementation details.

My point is that this is the solution to use and there really isn't any reason to switch. But, if you really were that bothered that you wanted to to switch, you aren't super tied to it in your codebase. I'm not saying the cost to switch is zero, I'm saying it isn't impossible.