Alter Glossary is Joomla5-native and can work without BC plugin.

Cool ! Hope all these extensions will soon be native Joomla 5 too!

Cheers!

... fonts in tips for Joomla 4. ⋅ Feature: new tip setting "Tip Hide Delay". ⋅ Fix: usage page delete broken in Joomla 3. ⋅ Feature: new setting "Glossary View > Subcategory Order" to order the list of subcategories differently from category order of terms. ⋅ Feature: glossary view search suggestions. ...

⋅ Fix: terms import with non-existing IDs. ⋅ Feature: new setting "Link Title" for Glossary view. Re-save component settings to link titles by default. ⋅ Feature: new setting "Show Alphabet Counts" displays number of terms per letter as tooltip. ⋅ Feature: filtered glossary letter is included in bread ...

09 August 2021 - ver. 3.4.0: ⋅ Feature: new term setting "Extra Words" helps to parse custom phrases. ⋅ Feature: new term setting "Custom Tip Title" to display custom title in term tip. ⋅ Feature: global "Term List" default settings in component options. ⋅ Feature: new term list setting "Term Style" ...

⋅ Fix: automatic term meta description not applied. ⋅ Fix: term keywords not saved. ⋅ Feature: new component setting "SEO > Block Meta Words" to exclude certain words from automatic meta keywords and description. ⋅ Feature: parsing speed improvement. ⋅ Feature: new parsing options "Highlight Synonym ...

⋅ Feature: new setting 'Highlight Permutations' allows to additionally highlight all collocation permutations, i.e. the term 'John Lennon' is parsed as 'Lennon John'. ⋅ Feature: custom layout overrides for tips via /templates/your-template/html/plg_system_aglossary/tips/ layouts. Read full article...

Thanks for your feedback, a review in JED is really appreciated

I bought both, the same day, three days ago.
At this point in time the situation is the following :
Alter Glossary is wayyyyy supperior.
Joomunited's product also is buggy right now.
Clear coice - speaking from experience here.