0. Mount iso-file Matlab98R2020a_Lin64.iso
1. Run "install" from mounted iso-file and if you see login/password/signin form (installer has access to internet)
     then in upper right corner in "Advanced Options" select setup mode "I have a File Installation Key"
     If internet access is absent then required setup mode will be autoselected and you do not need to set setup mode
2. When you will be asked to "Enter File Installation Key" enter
     09806-07443-53955-64350-21751-41297
3. When you will be asked to "Select License File" you can simply press "Next"
4. Then select folder where you want Matlab to be installed. When you will be asked to "Select products" select components you need.
     If you will leave all components selected matlab will need 32Gb of disk space and longer startup time.
     If you left only "MATLAB" - 3Gb of disk space
     You better setup matlab on SSD disk for better startup time, so most likely you do not want to waste SSD-disk size for nothing.
5. After installation is done copy file "libmwlmgrimpl.so" to already existing folder
     "<matlabfolder>\bin\glnxa64\matlab_startup_plugins\lmgrimpl"
     with overwriting of existing file (<matlabfolder> - is where you have installed Matlab)
6. Copy "license.lic" file to <matlabfolder>\licenses folder (create folder licenses if it does not exists)
     Alternatively you can just start Matlab. In that case you will got window asking you to select license
       First select "Activate manually without the Internet" and
       then in field "Enter the full path to your license file, including the file name" select "license.lic" file
7. Work with matlab :)

P.S.
license.lic additionally to possibilities of license_standalone.lic gives Matlab permission to work from remote desktop (RDP)
  This allow not to use license_server.lic in certain cases

P.S.2
File Installation Key you give to installer actually depend on Matlab edition and type of license you want
  For standalone license use license.lic or license_standalone.lic and keys:
    For workstation use case (typical configuration)  : 09806-07443-53955-64350-21751-41297
    For cluster node "Matlab Production Server"       : 40236-45817-26714-51426-39281
  For floating license use license_server.lic and keys:
    For workstation use case (typical configuration)  : 31095-30030-55416-47440-21946-54205
    For cluster node "Matlab Production Server"       : 57726-51709-20682-42954-31195