Now I even can't install any FHDB because 'mythical HDD issue, use HDDChecker'
I'm not sure which error you got, but such a message indicates that the content of the HDD could have some problem. Like it or not, your PS2's HDD's contents could be not quite sane.
Even if you chose to ignore it, it doesn't mean that other software can use it reliably.
Assuming it comes back whenever you run the installer, it could be that the __system partition is corrupted, which explains the HDD Browser not working. It could also be that the the partition was marked as bad because of a failed write. These errors can only be cleared by the HDD Utility Disc (or HDDChecker).
If you don't want to use HDDChecker for any reason, then you could also use the HDD Utility Disc, which was where I cloned the modules from.
Under normal use with the official software, the MBR program (which part of FHDB substitutes) will check that the HDD is usable, which includes checking for the S.M.A.R.T. status, whether any partitions have been flagged as damaged or whether the disk had encountered I/O errors before. By jumping straight to homebrew software, this whole process was just swept under the rug for most people.
which NEVER worked for me
Would you care to elaborate here?
it didn't even for my friend with 3 compatible HDDs that allow him to run FMCB 1.966 without issues but he can't install FHDB on any of his HDDs (all ATA).
Is he using a genuine Sony adaptor? If not, then the problem is possibly with his adaptor. Software like OPL had the ancient ATAD module design kept around for a really long time, which is why some people did not realize that their compatible adaptors are not actually so compatible. Some of them don't even work with the boot ROM's ATAD module, which prevents bootup from the HDD unit. Some others can't even be used to write data properly.
my friend is using FMCB 1.966 because similar issue just no modchip.
He had problems with FHDB, but you are having problems with FMCB right? Your modchip is making your PS2 non-standard, hence the compatibility problems that newer versions of FMCB have because of the new features.
Although both share similar names, the same logo and offer visibly similar functionalities, they operate with different devices and the both of you seem to be encountering different hardware problems.