This!
I paid for inSync when it was a yearly fee (three google accounts, all paid) and I gave my very negative feedback when the price model changed, first of all because it was really difficilt to understand the new one (communication was terrible, sorry guys).
I wondered how could you bear with the future without a constant money stream and I was worried for the quality of the product. And man, I was right… inSync 3.x is unusable and dangerous and after pinning 1.5 for a while on my Linux PCs I decided last time NOT to reinstall the software anymore.
Too bad the only alternative is running everything in the browser, which is really unfortunate.
If I had to suggest a pricing model, well keep it simple: affordable per-cloud-account yearly fee.
Since many here said they would never go with an yearly fee, maybe a more expansive one-off option that covers one major release (need to pay more to upgrade from 3 to 4 for example).
About freemium, it can pay off, but if I had to decide, please concentrate on doing one-thing better and ensuring you have the resources to spend on a PREMIUM product. Data are vital and inSync quality sunk to abysmal levels.
That’s a shame… 2020 and there is no RELIABLE way to sync files to the cloud from Linux.