Install Big Sur on a dual partition HFS drive keeping legacy booter?

[PhantOS]

Here's the situation:

 

256gb SSD, with two HFS partitions

Mavericks in the first, booting with legacy Chameleon

High Sierra in the second, UEFI booting with Clover (but Opencore works as well)

 

I'd like to install Big Sur instead of High Sierra in the second partition: will the forced APFS conversion destroy the legacy booter for Mavericks?

[PhantOS]

21 hours ago, Hervé said:

You cannot have 2 x bootloaders on the same disk. And Chameleon for Big Sur will be a no no.

But no problem with HFS + APFS on the same disk. Just complete the switchover to Clover or OpenCore, both will boot Mavericks and Big Sur.

 

Actually on this disk I had legacy Chameleon for Mavericks (with boot0 etc), and Clover in the EFI partition for High Sierra.

 

Unfortunately I didn't found a way to have Opencore boot the old Mavericks installation. All the old custom kexts are not in /Extra but in S/L/E, what should I remove there apart from FakeSMC since I'm replacing them with the new ones?

 

For future reference, converting the second partition to APFS didn't touch the MBR at the beginning of the disk at all, so both still work.

[PhantOS]

4 minutes ago, Hervé said:

I guess you don't have Chameleon in the ESP. Don't know how you switch between the 2 then. Through a BIOS boot menu?

Exactly! Any tips on getting Opencore to cooperate with Mavericks?