Since I can only reach a TTN gateway with my shield on the balcony, I’m looking for a solution for my project. That’s when I came across the TTNIG Gateway. Who has experience with this? Can I use this to improve my access misery? Can others in the neighborhood use this gateway and access my router with it?
Feel free to give me feedback with your experiences and recommendations.
thanks
I think you mean this, right?
https://www.thethingsnetwork.org/docs/gateways/thethingsindoor/
I have one of those. It is a fully functional gateway (has all 8 LoRa channels) and connects fine to the TTN infrastructure. It is for indoor use only and has an internal antenna. Being indoor and with an antenna like that is you will have coverage in/around your house but not much beyond that.
There are some known hacks with people adding an external antenna connector to the TTIG, making it possible to attach a different antenna. I guess this voids your warranty and you may be violating local radio regulations.
Another option with a similar price is the LPS8. This is basically a wifi router (openwrt) with a LoRa subsystem added. It already has an external antenna connector:
These are quite fine to put in a room next door to where you are developing nodes as a locally visible test GW or for general “indoor out” network deployments. I typically use them for infill deployments between larger, usually outdoor systems or for deployments where coverage is locally constrained e.g. by building clutter or terrain masking/local topology. I have liitle problem getting 2-6km in suburban and rural locales and have seen >20km for some. As mentioned there are hacks to use with external antenna, allow for cable/connector losses and dont go mad on ant gain and they stay within local RF power limits 
WiFi only. The LPS8 (and indeed its follow ons) also good as mentioned - v1 was quite cheap (less so these days in UK with poorer £/$ exchange rates!) and added deployment flexibility with ethernet connection as well as WiFi, both are SX1308 ‘value engineered’ 1st Gen Baseband device systems - Pico-reference design. If you want to stick with a Things device: The original Things Gateway aka the TTGW or The Things ‘Kickstarter’ Gateway -TTKGW, which uses the original full fat SX1301 is still available in limited quantities in some channels (no longer manufactured I dont think) as well as new on eBay (GIYF - “The Things Gateway EU (TTN-GW-868)”, or eBay The Things Gateway EU (TTN-GW-868): Search Result | eBay - note change the .co.uk to target your local country version usually works), has Wifi & Ethernet but is more expensive. I sometimes use these where I know I have the potential for greater range based on limited building clutter or clear LOS with reduced terrain masking - often see 10-20km and have seen >40km. External Ant, with option to therefore easily keep indoors in convenient place but with a short feed to better placed antenna location. There are a lot more - please use forum search for recommendations and suggestions and others experience, with many newer generation SX1302 or even SX1303 based systems out there at a range of price-points… all give broadly similar basic RF performance, with various alternate features - some of which arent used on e.g. TTN as yet such as lowers SF’s options etc., but may have reduced power consumption or value engineered spec’s. Just remember when it comes to GW coverage its a bit like the property market - most important is Location, Location, Location! Get it high (or atleast the Antenna!) and get line of sight (LOS) where you can… 
Good luck!
Yes they can use this gateway (and others) to send LoRaWAN packets to TTN (if you connect it to TTN). No they can not use it to gain access to your network or your router. The gateway will only forward data it receives from radiowaves to TTN your WiFi connection and transmit data it received from TTN to the radiowaves. There is no way to connect to any gateway using LoRaWAN, not like a WiFi router where you can access a user interface from WiFi.