How to obtain Egg Memos in Sonic Frontiers
We'll go through how to obtain each of the game's 24 Egg Memos, what they're used for, and maybe the biggest mystery of them all: how to view them in the confusing menu system.
How to get every Egg Memo
You'll need to fish a lot in Sonic Frontiers if you want to collect all 24 Eggs Memos. Big the Cat will sell them to you in exchange for fishing tokens, which you receive at random based on the catch you make at the Fishing Spot in each zone. You'll need to do a lot of fishing to get them all because, like any other item you may buy from Big, the price increases after you buy one or two. The first fishing spot is located on the western side of Kronos Island.
You must also pay Purple Coins each time you go fishing with Big the Cat, and the cost rises with each new location. These can be located by circling certain areas quickly and generally following tracks and jumps. Since there are many more Purple Coins to be found on Ares Island, I'd suggest using your Purple Coins from Kronos Island instead of Egg Memos on Portal Gears, Chaos Emerald Vault Keys, and Amy's Memory Tokens in order to get through the first zone more quickly. You can quickly travel(opens in new tab) back to Kronos Island and the initial Fishing Spot at any time by switching maps.
The only way to get to your Egg Memos is to ask Big the Cat and choose the fish-o-pedia option. When you are not at the fishing spot, there is no way to view them in your inventory or on any menu.
The Egg Memo collections may appear to serve a hidden agenda, but they are merely for flavor and mythology. When you buy one, you can listen to it, and it will play a brief snippet of Dr. Eggman discussing cyberspace. To get your Sonic lore fix, however, you can always just listen to them on YouTube, like in this video by Egg Emperor: If you don't want to bother getting them for yourself since they seem to have no in-game benefit.
Source: https://www.pcgamer.com/sonic-frontiers-egg-memo/ - Sean Martin