Last I checked Vsevolod Chaplin is a ROC clergy, even an Archpriest, and he is supporting Islamic banking system in Russia
https://www.novayagazeta.ru/articles/2016/01/26/67183-171-my-znaem-chto-dumaet-bog-187
Killing apostates is certainly not a founding principle of any Abrahamic religion Islam included.
Now you are changing the definitions. I would go so far as to say that one of the original principles for the Islamic system is to get rid of their apostates/deserters.
For instance even today Saudi Arabia has criminal statutes making it illegal for a Muslim to change religion or to renounce Islam, which is defined as apostasy and punishable by death. KSA is not alone: Afghanistan, Iran, Malaysia, Maldives, Mauritania, Nigeria, Qatar, Somalia, Sudan, United Arab Emirates, Yemen all have the same law.
In at least a further 7 countries, apostasy is punishable with a prison sentence: Bahrain, Brunei Darussalam, Comoros, Gambia, Iraq, Kuwait, Oman.
https://humanists.international/get-involved/resources/the-right-to-apostasy-in-the-world/
I might be wrong but think adultery is criminally illegal in some part of US too. That’s a similiar thing. In Russia adultery is only illegal in the Navy (or maybe not at this point) but that prompts nothing beyond disciplinary action.
That’s purely religious stuff within legal system.
As for Chaplin he is an excentric populist figure and not representative of all things Orthodox.
When it comes to Islam there is Dan Sysoyev who are on the opposite side.
Now I feel like you have appointed me the advocate of the devil but let’s play ths game further.
I personally believe Islam has no place in Europe or Americas but it makes perfect sense in Africa.
Just name some “semi-decent” African country and it is Islamic.
When you have universal poverty and 35 year life expectancy due to 40% HIV rate it makes perfect sense to chop hands and feet off thieves and carjackers and to stone adulterers or throw homosexuals off cliffs too.
It is a matter of human survival.