A company with a public offering basically cannot refuse a large enough buyout because with a public offering comes a financial responsibility to the shareholders. Public stock is a contract saying give me money and I’ll do my best to make you money back, and it’s very legally binding.
You can avoid this by never going public, but that also means you basically don’t get big investors for expanding what you can offer. A public offering involves losing some of your rights as owner for cash.
When the legal goal becomes “money above all else”, it is hard to justify NOT selling all the data and violating the trust of your customers for money, customer loyalty has to be monetizable and also worth more.
Proton has given a majority share to a nonprofit with a legal requirement to uphold the current values, not make money. This means that the remaining ownership can be sold to whoever, the only way anything gets done is if this foundation agrees. It prevents everything associated with a legal financial responsibility to make money, but still allows the business to do business things and make money, which seems to be proton’s founder’s belief, that the software should be sold to be sustainable.
If they’re still working, they don’t need your support. Focus on staying in touch with them, and let them know that if they do need you, you’re here.
Like someone else said, instead putting money into savings, so that a future need can come out of that instead of your current funds, that’ll mitigate the future need.