Would it be possible to choose which bootloader we want to use during installation? Maybe the Calamares installer could have an extra step, where you get to choose between GRUB, systemd-boot or rEFInd, instead of forcing the user to install EndeavourOS with GRUB only.
It is very easy to install refind after. There is also a tutorial for systemd boot. Right now there is no setup on the live ISO as far as i know.
The way Calamares works does not allow this. At least not easily. Calamares uses a config file for the bootloader to be installed, and that config file must be different for each bootloader. As it stands, the bootloader configuration file allows only one bootloader to be specified. In order to achieve what you want, three different bootloader configurations files must be present and only one of them can be loaded when Calamares runs. The devs would need to script this type of action into a Calamares pre-loader that asks which bootloader you want, then copy the right config file into place before Calamares is launched.
Actually, it would be simple to add a page to Calamares select the bootloader interactively. It is more a question of should we than can we.
How so? I did not know Calamares could accommodate that.
Calamares can be modified. You don’t have to just use it as is.
Just add a trivial module to make the selection and then have the modules read that instead of the config option. Those changes would take very little time. It would take longer to test than to implement.