I fear that things with ARM are likely to get worse if the EU approve the sale to NVIDIA. I don’t know of any SBC or SoC from ARM that is fully open, the closest would be the Raspberry Pi maybe. The Librem 5 is using off the shelf components to accomplish their goals, which means they have made a very heavy/bulky phone that is probably using some components designed for a laptop. I don’t personally mind if some devices use blobs, it is fine until they can reverse engineer and open source the drivers.
I think that in maybe 2 years the current Linux efforts will produce a usable system that can be used as a daily driver by enthusiast/power users - take this with a grain of salt as this is just my opinion. A Linux phone may be closer than we think, if we were to take the Ubuntu Touch OS as a base, but this depends on the interest of community and developers.
To sum things up though, I am very optimistic about the future. The Fairphone 4 has reignited my interest in phones and alternative OS, maybe this will be a device that helps us get there!