MySQL 5.5.57 No longer supports myisamck *.MYI I use 
    myisamchk *.MYI
to optimise all my tables.

However this no longer works with the MYI extension

# myisamchk mytable
Checking MyISAM file: mytable
Data records:   17952   Deleted blocks:       0
- check file-size
- check record delete-chain
- check key delete-chain
- check index reference
- check data record references index: 1

# myisamchk mytable.MYI
myisamchk: error: 140 when opening MyISAM-table 'mytable.MYI'
Still happening in MySQL 8.0.11

Walkarround solution: NOT USE THE MYI EXTENSION

myisamchk mytable