Is what I did, informing people about the da‘wah (Islamic propagation) topics I wrote and published online, whether with the intention of disseminating them or in the context of conversation, considered showing off (riya’)? This is despite the fact that the original intention was purely for the sake of Allah. And is it better for me to make my work available for everyone to copy and benefit from, or should I publish this work under my pseudonym online?

Hypocrisy (Riyaa’) is performing an action for people to see. As for informing about what you have done after completing it with sincerity to Allah Almighty, it is not considered hypocrisy. Rather, it is seeking reputation (Sum'ah) if you intend by it benefit, praise, or fame.

However, if the intention behind your informing is to spread the work so that the largest possible number of people can benefit from it, then this is not among the forbidden seeking of reputation; rather, it is an indication towards good.

Seeking reputation (Sum'ah) is informing about acts of obedience after they have been performed with sincerity, aiming for the purposes of hypocrisy. If a servant repents from seeking reputation, his عمل (deed) is not nullified, and he is forgiven.

It is preferable to use methods that facilitate benefiting from the work and conveying it widely, and there is no objection to that being under your known name or a pseudonym.