I have only heard start ups that really need to optimise cost by doing this. But big enterprises and finance companies haven't seen it happen most likely those companies don't really mind vendor lock-in for a nice discount.
I've had managers push for Blazor several times, despite the market of capable frontend devs who know/can learn JS being far bigger, and the technologies being more mature and proven. They aren't worried about vendor lock-in, they encourage it.
It's a shame too. Much of their tech is great, but we are seeing several of the good old M$ shenanigans popping up again, after their 'big open source' push.
C# is still king, but it’s been getting a few features from F# the past few years.
Also, Microsoft are all-in on cloud stuff; this is where they are placing their bets. accordingly, Windows server and client operating system strategy are not designed to lock you in any longer, certainly not like they were 20 years ago. It was awful when they were, and they don't really care much about those in comparison to the past.
Microsoft want you to be a Microsoft 365 customer and they want you to be an Azure customer.
You can natively run lots of Linux distributions inside Windows, which cleanly integrate with the host Windows OS and Microsoft promote this as a first-class way to develop software for Linux and Windows. This is the opposite of lock-in.
Azure Linux is a Linux you might choose if you are already on Azure. You are not required to use Azure Linux when using Azure, or anything else.
"oh no, Microsoft have released a free Linux distro and are abiding by license terms!! LOCK IN!!" Come on.
While I agree with the spirit of your post, I think k8s is a great counterexample. Of course there is a ton of things that is vendor dependent, and you can be sure each vendor will try to exploit that, but overall it's the closest thing to avoiding vendor lock-in that we have now.
Maybe 2 years ago I'd hesitate to say that as k8s was just a part of the equation but now that I've been successfully running a Postgres operator without any problems for a couple of months I feel it finally feels like a more complete solution that you can deploy in any environment in a way that is an order of magnitude (or two) faster than traditional migration from one environment to another. Specifically, it lets you avoid many services that are called "cloud-native" which basically means "harder to migrate from".