Ryzen 5 5600 or i5-12400F for a budget DDR4 build?

I'd compare the total cost of the CPU and a suitable motherboard, not just the chip prices. The 5600 and 12400F are close enough in performance that a good local deal could make the choice for you.

If you're planning to replace the platform later anyway, I wouldn't pay much extra for an upgrade path you may never use. Check bundles too, if any are available where you live.

One correction that might help: both CPUs have six cores and twelve threads. The 12400F doesn't have extra cores over the 5600.

Also, the F model has no integrated graphics, so you don't get Intel Quick Sync for video encoding. A non-F Intel CPU is worth considering if your editing software can use Quick Sync and the price fits, but don't buy the 12400F expecting that feature.

I'd lean toward the 12400F if you can find a well-priced DDR4 motherboard for it. It's a solid budget option for both work and games. Just make sure the board you choose takes DDR4, since LGA 1700 boards come in both DDR4 and DDR5 versions.

The 5600 would be my pick if AM4 boards are cheaper in your area. It's a capable gaming chip, and there's no need to stretch the budget for a small difference between these two.

AM4 upgrades could be an option later, but availability and prices vary by country. Check what's actually for sale before counting that as an advantage.

If you're considering a later LGA 1700 upgrade, look at the available CPUs and their prices rather than assuming every 13th or 14th generation model has the same reliability concerns. A 14400F has more cores than the 12400F, though whether it's worth the extra cost depends on your work and local pricing.