@Pendululuman
Have the same problem. I dig up the file and found that the exploration idea is missing "quest_for_the_new_world". and the ability for any nation to get explorer.

Quick fix is
1. to go to steamapps\workshop\content\236850\3122839484\common\ideas
2. Then edit the "btc_basic_ideas.txt" file with notepad.
3. Find the exploration idea ( search: exploration_ideas = { )

4. Replace the 1st idea with the following text.

quest_for_the_new_world = {
may_explore = yes
naval_attrition = -0.1
}

NOTE: Afterward, it should look like this.

bonus = {
cb_on_overseas = yes
monthly_portuguese_saudade = 0.075
}

quest_for_the_new_world = {
may_explore = yes
naval_attrition = -0.1
}

colonial_ventures = {
colonists = 1
}

Playing as the Ottobros, whenever colonialism spawns and I navigate to the Institutions screen, the game crashes. I think I notice that the colonialism does not spread anywhere.

Thank you for the report. Already working on fixing a few bugs that were found. If you see anything else please let me know

The idea "Camp Followers" in Mobilization ideas gives two negative modifiers when it doesn't seem like its supposed to