Given there is more stuff you could learn than you will ever have time to, you'll need to prioritise, so I would look at the types of "hard" software problems you need to constantly deal with, because architecture is all about making decisions on hard problems.
These problems could come in the shape of:
Pick any/all of these and look broadly at how other people/teams/organisations are solving these problems. Try to move between technical and problem domains frequently (several each year) to build up good broad experience, to compliment your existing deep experience.
p.s Architectural skill does not necessarily imply deeper knowledge
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