Thank you for the answers.
So, to whom it may concern, here's a brief report. I installed linux-lts by first running this command to always display the Solus startup menu:
sudo clr-boot-manager set-timeout 5 && sudo clr-boot-manager update
Then, just using Software Center, I checked what modules listed here I have installed. It turned out, none. Also, FYI, nvidia-340-glx-driver and razer-drivers are no longer in the repository at all.
Next, I installed the LTS kernel by just running:
sudo eopkg install linux-lts
I rebooted. USB devices do work under LTS kernel, but there's still the damn delay before they become active. Around 30 seconds, when the OS is already started. Not sure what to do with this.
Anyway, if you want to make the currently booted kernel your permanent choice, here's what you need to do:
After successfully booting into a kernel from the current or lts branches running sudo clr-boot-manager update will make the booted kernel branch the default boot option going forward.
