Both words are frequently used in Bengali with the same meaning, and we use both of them on Mediawiki as well.
So both words have been added as namespace aliases in all talk namespaces.

Newly added aliases

'আলোচনা' => NS_TALK,
'মিডিয়াউইকি_আলাপ' => NS_MEDIAWIKI_TALK,
'টেমপ্লেট_আলাপ' => NS_TEMPLATE_TALK,
'সাহায্য_আলাপ' => NS_HELP_TALK,
'বিষয়শ্রেণী_আলাপ' => NS_CATEGORY_TALK,
'ব্যবহারকারী_আলোচনা' => NS_USER_TALK

• Related discussion: https://w.wiki/72yy