That message is probably talking about PC Companion. Unless you've set the phone not to do it, it'll try to install the tool every time it connects to the computer.
You can't use PC Companion to update your phone once it has an unlocked bootloader but you might be able to do it with Emma. That's a flashtool made by Sony for unlocked bootloaders only.
Sent from my Sony Xperia XA1 using XDA Labs
Yeah, you are right. I did hear about Emma, very interesting...
However, for a newly released device, current support and development is good.
Thanks to janjan we already have recovery and root, already a huge step ahead...
To be honest, in many cases it takes months for root to be acquired so cannot complain.
In fact, very soon we'll probably see mods and even custom roms...
I'm quite surprised in another way, the screen is hands down AMAZING on this phone, sharpness and colour.
I played some ultra HD videos on both my XA1 Ultra & my Xiaomi Mi Mix, both having the same quality 1080P screen.
Very easily the Sony is far sharper and punchier colours. Just as all the reviews said, even though the XA1 Ultra is only a mid ranger, the screen is better than other high end flagships such as the XZ Ultra...