Do Pokemon stay ‘super shiny’ when they evolve

The Shiny Charm returns once again this Generation and increases the regular encounter shiny rate from 1 in 4096 to 1 in 1365.3. It can be obtained by completing the Pokedex and then talking to a doctor within a room on the 2nd floor of Hotel Ionia in Circhester. The Masuda method has also returned with no significant changes as far as we know. Chaining however has been replaced by a new system:

The more times you've defeated a certain species of Pokemon in battle, the higher your chances are of finding a shiny of that species, with the best odds being at 500+ battles. These battles do not have to be in a row (chained) to receive these increased odds. You can keep track of how many times you've battled a certain species of Pokemon from their Pokedex entries as it has a counter. For example, at 500+ battles won against one species, your chances of getting a shiny are increased to 1 in 683 (1 in 512 with the Shiny Charm). The graph at the bottom of this page should help. *

*Serebii, which has been a reliable source of Pokemon information for years, is claiming it's possible there's a bug in the code causing the new shiny hunting method not to be anywhere near as effective as it should be. In the table linked you linked there is a "Chance of Shiny Rate" column. This column shows that at 500+ encounters you only have a 3% chance of receiving the boosted 1 in 683 odds. Serebii has also confirmed that's what the column means on their official Reddit account. Just some anecdotal data from me, I reached 6000 encounters of the same Pokemon without finding a shiny. And from YouTubers I watch they seem to be having much more luck with the Masuda method. So I'd stick to Masuda for now if I were you.

There are plenty of trades to perform in Sword/Shield! Here's the ones I've been able to find, as well as some from other sources

Both Games:

These trades are available in both games:

1. Bunnelby → Skwovet ♂ (Motostoke Pokemon Center)
   _{Nickname: Cheekers, Level: 10, Nature: Mild, Ability: Cheek Pouch, Held Item: Oran Berry, Dynamax: 1}

   • Tackle
   • Tail Whip
   • Bite
   • Stuff Cheeks

2. Meowth (Galar) → Meowth (Kanto) ♂ (Turrfield Gym)
   _{Nickname: Cash, Level: 18, Nature: Timid, Ability: Technician, Held Item: Sitrus Berry, Dynamax: 1}

   • Scratch
   • Pay Day
   • Bite
   • Last Resort

3. Minccino → Cottonee ♀ (Hulbury Market)
   _{Nickname: Candyfloss, Level: 23, Nature: Modest, Ability: Prankster, Held Item: None, Dynamax: 1}

   • Mega Drain
   • Razor Leaf
   • Growth
   • Last Resort

4. Toxel → Togepi ♀ (Hammerlocke - Outside Vault)
   _{Nickname: Snips, Level: 25, Nature: Timid, Ability: Serene Grace, Held Item: None, Dynamax: 1}

   • Ancient Power
   • Yawn
   • Metronome
   • Life Dew

5. Yamask (Galar) → Yamask (Unova) ♂ (Ballonlea Gym)
   _{Nickname: Masky, Level: 36, Nature: Bold, Ability: Mummy, Held Item: None, Dynamax: 2}

   • Hex
   • Mean Look
   • Grudge
   • Will-O-Wisp

6. Obstagoon → Mr. Mime (Kanto) ♂ (Spikemuth - Near battle area)
   _{Nickname: Mymo, Level: 40, Nature: Calm, Ability: Soundproof, Held Item: None, Dynamax: 1}

   • Light Screen
   • Reflect
   • Safeguard
   • Sucker Punch

7. Frosmoth → Duraludon ♂ (Wyndon - 4th house down from the stadium)
   _{Nickname: Linear, Level: 50, Nature: Adamant, Ability: Heavy Metal, Held Item: None, Dynamax: 3}

   • Iron Defense
   • Laser Focus
   • Dragon Claw
   • Night Slash

Version-Exclusive Trades:

These trades are exclusive to either Sword or Shield as noted below:

1. (Sword) Maractus → Hatenna ♀ (Stow-on-Side - Top of leftmost building)
   _{Nickname: Fringe, Level: 30, Nature: Quiet, Ability: Anticipation, Held Item: None, Dynamax: 1}

   • Aromatherapy
   • Psybeam
   • Heal Pulse
   • Dazzling Gleam

2. (Shield) Maractus → Impidimp ♂ (Stow-on-Side - Top of leftmost building)
   _{Nickname: Peepers, Level: 30, Nature: Random, Ability: Anticipation, Held Item: None, Dynamax: 1}

   • Assurance
   • Swagger
   • Sucker Punch
   • Torment

3. (Sword) Vanillish → Throh ♂ (Circhester - Ice cream stall)
   _{Nickname: Reddos, Level: 37, Nature: Adamant, Ability: Inner Focus, Held Item: None, Dynamax: 2}

   • Revenge
   • Bulk Up
   • Storm Throw
   • Vital Throw

4. (Shield) Vanillish → Sawk ♂ (Circhester - Ice cream stall)
   _{Nickname: Bluebop, Level: 37, Nature: Adamant, Ability: Inner Focus, Held Item: None, Dynamax: 2}

   • Low Sweep
   • Bulk Up
   • Retaliate
   • Brick Break

Sources for the ones I was unable to find originally:

• Serebii (Version exclusive differences for Shield)
• IGN