7 files declare their use of LineItemPluginBase in Ubercart 8.4

Generic.php in uc_order/src/Plugin/Ubercart/LineItem/Generic.php

Shipping.php in shipping/uc_quote/src/Plugin/Ubercart/LineItem/Shipping.php

Subtotal.php in uc_order/src/Plugin/Ubercart/LineItem/Subtotal.php

Tax.php in uc_tax/src/Plugin/Ubercart/LineItem/Tax.php

TaxDisplay.php in uc_tax/src/Plugin/Ubercart/LineItem/TaxDisplay.php

TaxSubtotal.php in uc_tax/src/Plugin/Ubercart/LineItem/TaxSubtotal.php

Total.php in uc_order/src/Plugin/Ubercart/LineItem/Total.php